England’s Justin Rose, Canadian David Hearn and Americans Blayne Barber and Jerry Kelly were a further stroke back but no player in the field had completed more than 12 holes when play was suspended for the day in fading light.
Better weather is forecast for the New Orleans area on Sunday when organisers hope to conclude the tournament. Tee times for the final round have been scheduled for between 10 a.m. local (1500 GMT) and 12 noon.
“Fifty-four holes is not in the mix,” Slugger White, the PGA Tour’s vice president of rules and competitions, told reporters.
White said the goal was to complete the tournament as scheduled but added that, if further bad weather intervened on Sunday, “we would be here Monday if we have (lengthy) delays.”
Earlier on Saturday, Australian Day birdied two of his last four holes after play resumed in the weather-delayed second round to card a seven-under 65 and seize a one-shot lead.
The highest-ranked player in the field at the TPC Louisiana, Day drained a 34-footer at the par-four 15th before signing off with a tap-in from inside two feet at the par-five last.
“It’s taken a while but we got it in,” Day, who won his third career title on the PGA Tour with a playoff victory at the Farmers Insurance Open in February, told Golf Channel about the weather-disrupted second round.
“I came out today and played some really nice golf. Just happy where I’m at, I’m enjoying myself and hopefully the (bad) weather can stay away.”
Day’s 65 left him at 12-under 132, a stroke in front of Americans Hudson Swafford (66), Daniel Berger (67) and Chris Stroud (66).
Swafford had completed his 66 on Friday before approaching thunderstorms forced play to be suspended for the day with the afternoon wave of players still out on the course.
Berger and Stroud each recorded one birdie in their last three holes on Saturday morning to edge up the leaderboard.
The third round began soon after but further thunderstorms forced play to be suspended at 12.14 p.m. local time, wiping out nearly five hours of the day’s play.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Ian Ransom)